For the second experiment, the mutant and wild type cDNA was constructed. The cDNAs and GST genes were inserted into an expression vector. This stage was carried out to synthesize fusion proteins of LHX3a, LHX3bY116C, LHX3aY111C and LHX3b all fused to GST. Glutathione S-transferase (GST) is known to be a protein which aids in the purification and isolation of proteins of interest. The controls were set up by isolating the GST proteins only. The fusion proteins were later separated with the use of electrophoresis and the proteins were used as a substrate for the binding assay. Purified radio-labeled Pit-1 and NIL were later added to the gel that had the mutant and wild type fusion proteins.In this case, if there were binding sites(No mutation effect), the Pit-1 and NIL proteins could bind to the proteins(LHX3).The presence of the bound Pit-1 and NIL were visualized with fluorography. The binding of Pit-1 and NIL were then quantified by scintillation counting (electrophoresis gel band intensity measurement).
The first experiment aimed at determining if mutations in the LXH3 gene can interfere with LHX3a and LHX3b’s ability to binding to DNA promoters and reporter genes. As indicated in figure 1, both mutation types affected the activation of alpha GSU gene (red bars). The truncated mutations with no DNA binding domain were not able to activate the reporter gene, while on the other hand, point mutations with altered amino acid in the LHX3 protein interaction domain, had reduced activation.